content: /* Copyright (C) 2016-2018 Alibaba Group Holding Limited
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  ==============================================================================*/
  
  // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import static com.google.protobuf.Internal.checkNotNull;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * Internal representation of map fields in generated messages.
   *
   * This class supports accessing the map field as a {@link Map} to be used in
   * generated API and also supports accessing the field as a {@link List} to be
   * used in reflection API. It keeps track of where the data is currently stored
   * and do necessary conversions between map and list.
   *
   * This class is a protobuf implementation detail. Users shouldn't use this
   * class directly.
   *
   * THREAD-SAFETY NOTE: Read-only access is thread-safe. Users can call getMap()
   * and getList() concurrently in multiple threads. If write-access is needed,
   * all access must be synchronized.
   */
  public class MapField<K, V> implements MutabilityOracle {
    /**
     * Indicates where the data of this map field is currently stored.
     *
     * MAP: Data is stored in mapData.
     * LIST: Data is stored in listData.
     * BOTH: mapData and listData have the same data.
     *
     * When the map field is accessed (through generated API or reflection API),
     * it will shift between these 3 modes:
     *
     *          getMap()   getList()   getMutableMap()   getMutableList()
     *   MAP      MAP        BOTH          MAP               LIST
     *   LIST     BOTH       LIST          MAP               LIST
     *   BOTH     BOTH       BOTH          MAP               LIST
     *
     * As the map field changes its mode, the list/map reference returned in a
     * previous method call may be invalidated.
     */
    private enum StorageMode {MAP, LIST, BOTH}
  
    private volatile boolean isMutable;
    private volatile StorageMode mode;
    private MutatabilityAwareMap<K, V> mapData;
    private List<Message> listData;
  
    // Convert between a map entry Message and a key-value pair.
    private static interface Converter<K, V> {
      Message convertKeyAndValueToMessage(K key, V value);
      void convertMessageToKeyAndValue(Message message, Map<K, V> map);
  
      Message getMessageDefaultInstance();
    }
  
    private static class ImmutableMessageConverter<K, V> implements Converter<K, V> {
      private final MapEntry<K, V> defaultEntry;
      public ImmutableMessageConverter(MapEntry<K, V> defaultEntry) {
        this.defaultEntry = defaultEntry;
      }
  
      @Override
      public Message convertKeyAndValueToMessage(K key, V value) {
        return defaultEntry.newBuilderForType().setKey(key).setValue(value).buildPartial();
      }
  
      @Override
      @SuppressWarnings("unchecked")
      public void convertMessageToKeyAndValue(Message message, Map<K, V> map) {
        MapEntry<K, V> entry = (MapEntry<K, V>) message;
        map.put(entry.getKey(), entry.getValue());
      }
  
      @Override
      public Message getMessageDefaultInstance() {
        return defaultEntry;
      }
    }
  
  
    private final Converter<K, V> converter;
  
    private MapField(
        Converter<K, V> converter,
        StorageMode mode,
        Map<K, V> mapData) {
      this.converter = converter;
      this.isMutable = true;
      this.mode = mode;
      this.mapData = new MutatabilityAwareMap<K, V>(this, mapData);
      this.listData = null;
    }
  
    private MapField(
        MapEntry<K, V> defaultEntry,
        StorageMode mode,
        Map<K, V> mapData) {
      this(new ImmutableMessageConverter<K, V>(defaultEntry), mode, mapData);
    }
  
  
    /** Returns an immutable empty MapField. */
    public static <K, V> MapField<K, V> emptyMapField(
        MapEntry<K, V> defaultEntry) {
      return new MapField<K, V>(
          defaultEntry, StorageMode.MAP, Collections.<K, V>emptyMap());
    }
  
  
    /** Creates a new mutable empty MapField. */
    public static <K, V> MapField<K, V> newMapField(MapEntry<K, V> defaultEntry) {
      return new MapField<K, V>(
          defaultEntry, StorageMode.MAP, new LinkedHashMap<K, V>());
    }
  
  
    private Message convertKeyAndValueToMessage(K key, V value) {
      return converter.convertKeyAndValueToMessage(key, value);
    }
  
    @SuppressWarnings("unchecked")
    private void convertMessageToKeyAndValue(Message message, Map<K, V> map) {
      converter.convertMessageToKeyAndValue(message, map);
    }
  
    private List<Message> convertMapToList(MutatabilityAwareMap<K, V> mapData) {
      List<Message> listData = new ArrayList<Message>();
      for (Map.Entry<K, V> entry : mapData.entrySet()) {
        listData.add(
            convertKeyAndValueToMessage(
                entry.getKey(), entry.getValue()));
      }
      return listData;
    }
  
    private MutatabilityAwareMap<K, V> convertListToMap(List<Message> listData) {
      Map<K, V> mapData = new LinkedHashMap<K, V>();
      for (Message item : listData) {
        convertMessageToKeyAndValue(item, mapData);
      }
      return new MutatabilityAwareMap<K, V>(this, mapData);
    }
  
    /** Returns the content of this MapField as a read-only Map. */
    public Map<K, V> getMap() {
      if (mode == StorageMode.LIST) {
        synchronized (this) {
          if (mode == StorageMode.LIST) {
            mapData = convertListToMap(listData);
            mode = StorageMode.BOTH;
          }
        }
      }
      return Collections.unmodifiableMap(mapData);
    }
  
    /** Gets a mutable Map view of this MapField. */
    public Map<K, V> getMutableMap() {
      if (mode != StorageMode.MAP) {
        if (mode == StorageMode.LIST) {
          mapData = convertListToMap(listData);
        }
        listData = null;
        mode = StorageMode.MAP;
      }
      return mapData;
    }
  
    public void mergeFrom(MapField<K, V> other) {
      getMutableMap().putAll(MapFieldLite.copy(other.getMap()));
    }
  
    public void clear() {
      mapData = new MutatabilityAwareMap<K, V>(this, new LinkedHashMap<K, V>());
      mode = StorageMode.MAP;
    }
  
    @SuppressWarnings("unchecked")
    @Override
    public boolean equals(Object object) {
      if (!(object instanceof MapField)) {
        return false;
      }
      MapField<K, V> other = (MapField<K, V>) object;
      return MapFieldLite.<K, V>equals(getMap(), other.getMap());
    }
  
    @Override
    public int hashCode() {
      return MapFieldLite.<K, V>calculateHashCodeForMap(getMap());
    }
  
    /** Returns a deep copy of this MapField. */
    public MapField<K, V> copy() {
      return new MapField<K, V>(
          converter, StorageMode.MAP, MapFieldLite.copy(getMap()));
    }
  
    /** Gets the content of this MapField as a read-only List. */
    List<Message> getList() {
      if (mode == StorageMode.MAP) {
        synchronized (this) {
          if (mode == StorageMode.MAP) {
            listData = convertMapToList(mapData);
            mode = StorageMode.BOTH;
          }
        }
      }
      return Collections.unmodifiableList(listData);
    }
  
    /** Gets a mutable List view of this MapField. */
    List<Message> getMutableList() {
      if (mode != StorageMode.LIST) {
        if (mode == StorageMode.MAP) {
          listData = convertMapToList(mapData);
        }
        mapData = null;
        mode = StorageMode.LIST;
      }
      return listData;
    }
  
    /**
     * Gets the default instance of the message stored in the list view of this
     * map field.
     */
    Message getMapEntryMessageDefaultInstance() {
      return converter.getMessageDefaultInstance();
    }
  
    /**
     * Makes this list immutable. All subsequent modifications will throw an
     * {@link UnsupportedOperationException}.
     */
    public void makeImmutable() {
      isMutable = false;
    }
  
    /**
     * Returns whether this field can be modified.
     */
    public boolean isMutable() {
      return isMutable;
    }
  
    /* (non-Javadoc)
     * @see com.google.protobuf.MutabilityOracle#ensureMutable()
     */
    @Override
    public void ensureMutable() {
      if (!isMutable()) {
        throw new UnsupportedOperationException();
      }
    }
  
    /**
     * An internal map that checks for mutability before delegating.
     */
    private static class MutatabilityAwareMap<K, V> implements Map<K, V> {
      private final MutabilityOracle mutabilityOracle;
      private final Map<K, V> delegate;
  
      MutatabilityAwareMap(MutabilityOracle mutabilityOracle, Map<K, V> delegate) {
        this.mutabilityOracle = mutabilityOracle;
        this.delegate = delegate;
      }
  
      @Override
      public int size() {
        return delegate.size();
      }
  
      @Override
      public boolean isEmpty() {
        return delegate.isEmpty();
      }
  
      @Override
      public boolean containsKey(Object key) {
        return delegate.containsKey(key);
      }
  
      @Override
      public boolean containsValue(Object value) {
        return delegate.containsValue(value);
      }
  
      @Override
      public V get(Object key) {
        return delegate.get(key);
      }
  
      @Override
      public V put(K key, V value) {
        mutabilityOracle.ensureMutable();
        checkNotNull(key);
        checkNotNull(value);
        return delegate.put(key, value);
      }
  
      @Override
      public V remove(Object key) {
        mutabilityOracle.ensureMutable();
        return delegate.remove(key);
      }
  
      @Override
      public void putAll(Map<? extends K, ? extends V> m) {
        mutabilityOracle.ensureMutable();
        for (K key : m.keySet()) {
          checkNotNull(key);
          checkNotNull(m.get(key));
        }
        delegate.putAll(m);
      }
  
      @Override
      public void clear() {
        mutabilityOracle.ensureMutable();
        delegate.clear();
      }
  
      @Override
      public Set<K> keySet() {
        return new MutatabilityAwareSet<K>(mutabilityOracle, delegate.keySet());
      }
  
      @Override
      public Collection<V> values() {
        return new MutatabilityAwareCollection<V>(mutabilityOracle, delegate.values());
      }
  
      @Override
      public Set<java.util.Map.Entry<K, V>> entrySet() {
        return new MutatabilityAwareSet<Entry<K, V>>(mutabilityOracle, delegate.entrySet());
      }
  
      @Override
      public boolean equals(Object o) {
        return delegate.equals(o);
      }
  
      @Override
      public int hashCode() {
        return delegate.hashCode();
      }
  
      @Override
      public String toString() {
        return delegate.toString();
      }
  
      /**
       * An internal collection that checks for mutability before delegating.
       */
      private static class MutatabilityAwareCollection<E> implements Collection<E> {
        private final MutabilityOracle mutabilityOracle;
        private final Collection<E> delegate;
  
        MutatabilityAwareCollection(MutabilityOracle mutabilityOracle, Collection<E> delegate) {
          this.mutabilityOracle = mutabilityOracle;
          this.delegate = delegate;
        }
  
        @Override
        public int size() {
          return delegate.size();
        }
  
        @Override
        public boolean isEmpty() {
          return delegate.isEmpty();
        }
  
        @Override
        public boolean contains(Object o) {
          return delegate.contains(o);
        }
  
        @Override
        public Iterator<E> iterator() {
          return new MutatabilityAwareIterator<E>(mutabilityOracle, delegate.iterator());
        }
  
        @Override
        public Object[] toArray() {
          return delegate.toArray();
        }
  
        @Override
        public <T> T[] toArray(T[] a) {
          return delegate.toArray(a);
        }
  
        @Override
        public boolean add(E e) {
          // Unsupported operation in the delegate.
          throw new UnsupportedOperationException();
        }
  
        @Override
        public boolean remove(Object o) {
          mutabilityOracle.ensureMutable();
          return delegate.remove(o);
        }
  
        @Override
        public boolean containsAll(Collection<?> c) {
          return delegate.containsAll(c);
        }
  
        @Override
        public boolean addAll(Collection<? extends E> c) {
          // Unsupported operation in the delegate.
          throw new UnsupportedOperationException();
        }
  
        @Override
        public boolean removeAll(Collection<?> c) {
          mutabilityOracle.ensureMutable();
          return delegate.removeAll(c);
        }
  
        @Override
        public boolean retainAll(Collection<?> c) {
          mutabilityOracle.ensureMutable();
          return delegate.retainAll(c);
        }
  
        @Override
        public void clear() {
          mutabilityOracle.ensureMutable();
          delegate.clear();
        }
  
        @Override
        public boolean equals(Object o) {
          return delegate.equals(o);
        }
  
        @Override
        public int hashCode() {
          return delegate.hashCode();
        }
  
        @Override
        public String toString() {
          return delegate.toString();
        }
      }
  
      /**
       * An internal set that checks for mutability before delegating.
       */
      private static class MutatabilityAwareSet<E> implements Set<E> {
        private final MutabilityOracle mutabilityOracle;
        private final Set<E> delegate;
  
        MutatabilityAwareSet(MutabilityOracle mutabilityOracle, Set<E> delegate) {
          this.mutabilityOracle = mutabilityOracle;
          this.delegate = delegate;
        }
  
        @Override
        public int size() {
          return delegate.size();
        }
  
        @Override
        public boolean isEmpty() {
          return delegate.isEmpty();
        }
  
        @Override
        public boolean contains(Object o) {
          return delegate.contains(o);
        }
  
        @Override
        public Iterator<E> iterator() {
          return new MutatabilityAwareIterator<E>(mutabilityOracle, delegate.iterator());
        }
  
        @Override
        public Object[] toArray() {
          return delegate.toArray();
        }
  
        @Override
        public <T> T[] toArray(T[] a) {
          return delegate.toArray(a);
        }
  
        @Override
        public boolean add(E e) {
          mutabilityOracle.ensureMutable();
          return delegate.add(e);
        }
  
        @Override
        public boolean remove(Object o) {
          mutabilityOracle.ensureMutable();
          return delegate.remove(o);
        }
  
        @Override
        public boolean containsAll(Collection<?> c) {
          return delegate.containsAll(c);
        }
  
        @Override
        public boolean addAll(Collection<? extends E> c) {
          mutabilityOracle.ensureMutable();
          return delegate.addAll(c);
        }
  
        @Override
        public boolean retainAll(Collection<?> c) {
          mutabilityOracle.ensureMutable();
          return delegate.retainAll(c);
        }
  
        @Override
        public boolean removeAll(Collection<?> c) {
          mutabilityOracle.ensureMutable();
          return delegate.removeAll(c);
        }
  
        @Override
        public void clear() {
          mutabilityOracle.ensureMutable();
          delegate.clear();
        }
  
        @Override
        public boolean equals(Object o) {
          return delegate.equals(o);
        }
  
        @Override
        public int hashCode() {
          return delegate.hashCode();
        }
  
        @Override
        public String toString() {
          return delegate.toString();
        }
      }
  
      /**
       * An internal iterator that checks for mutability before delegating.
       */
      private static class MutatabilityAwareIterator<E> implements Iterator<E> {
        private final MutabilityOracle mutabilityOracle;
        private final Iterator<E> delegate;
  
        MutatabilityAwareIterator(MutabilityOracle mutabilityOracle, Iterator<E> delegate) {
          this.mutabilityOracle = mutabilityOracle;
          this.delegate = delegate;
        }
  
        @Override
        public boolean hasNext() {
          return delegate.hasNext();
        }
  
        @Override
        public E next() {
          return delegate.next();
        }
  
        @Override
        public void remove() {
          mutabilityOracle.ensureMutable();
          delegate.remove();
        }
  
        @Override
        public boolean equals(Object obj) {
          return delegate.equals(obj);
        }
  
        @Override
        public int hashCode() {
          return delegate.hashCode();
        }
  
        @Override
        public String toString() {
          return delegate.toString();
        }
      }
    }
  }
  